Curve fitting (polyfit, fit) in MATLAB - Mini Project: Build & Apply

Curve fitting with polyfit and fit in MATLAB

📖 Scenario: You are working as a data analyst. You have collected some measurements of temperature and ice cream sales. You want to find a simple curve that best matches the data points to understand the trend.

🎯 Goal: Build a MATLAB script that fits a straight line to the data points using polyfit and fit functions, then display the fitted line.

📋 What You'll Learn

Create vectors for temperature and sales data

Create a variable for the degree of the polynomial fit

Use polyfit to find the coefficients of the best fit line

Use fit function to fit a linear model

Plot the original data and the fitted line

Display the coefficients and the fit result

💡 Why This Matters

🌍 Real World

Curve fitting helps understand trends in data like sales, temperature, or scientific measurements.

💼 Career

Data analysts and engineers use curve fitting to model relationships and make predictions.

1

Create the data vectors

Create two vectors called temperature and sales with these exact values: temperature = [15, 18, 21, 24, 27, 30] and sales = [200, 220, 250, 270, 300, 320].

MATLAB

% Create vectors for temperature and sales data
% Your code here

Need a hint?

Use square brackets to create vectors and separate values with commas.

2

Set the polynomial degree

Create a variable called degree and set it to 1 to indicate a linear fit.

MATLAB

temperature = [15, 18, 21, 24, 27, 30];
sales = [200, 220, 250, 270, 300, 320];
% Set the polynomial degree for fitting
% Your code here

Need a hint?

Use a simple assignment to create the variable degree.

3

Fit the data using polyfit and fit

Use polyfit with temperature, sales, and degree to get coefficients in a variable called coeffs. Then use fit with temperature', sales', and 'poly1' to get a fit object called fitresult.

MATLAB

temperature = [15, 18, 21, 24, 27, 30];
sales = [200, 220, 250, 270, 300, 320];
degree = 1;
% Use polyfit to find coefficients
% Use fit to get a fit object
% Your code here

Need a hint?

Remember to transpose vectors for fit using '.

4

Display and plot the results

Use disp to show coeffs and fitresult. Then plot temperature vs sales as points and overlay the fitted line using plot with temperature and polyval(coeffs, temperature). Add a legend and labels.

MATLAB

temperature = [15, 18, 21, 24, 27, 30];
sales = [200, 220, 250, 270, 300, 320];
degree = 1;
coeffs = polyfit(temperature, sales, degree);
fitresult = fit(temperature', sales', 'poly1');
% Display coefficients and fitresult
% Plot data points and fitted line
% Your code here

Need a hint?

Use disp to show variables and plot to draw points and lines. Use hold on and hold off to combine plots.